(33) The Oral Biome of the Multiple Sclerosis Patient: What Can the Oral and Maxillofacial Surgeon Do to Help?

Abstract: Statement of the problem:Changes in the microbiome can provide information about disease progression, severity, and drug efficacy and can contribute to disease by changing levels of active metabolites. Most studies look at the gut biome by examining fecal samples. However, differences also occur in the oral biome for example between Alzheimer’s disease and non-neurological controls (Bouftas et al. 2021). Using saliva samples, we previously showed differences in the oral biome of identical twins who had divergent multiple sclerosis (MS) severity (Boullerne et al. 2020). The goal of this study is to confirm differences in a larger cohort of subjects and determine how salivary metabolites are affected. Materials and methods:In this study we collect saliva samples from a total of 80 subjects (20 MS and 20 control; both White and African American). After 1 year, we collect a follow-up sample. After consent, subjects undergo a dental exam to record signs of disease, count cavities, missing teeth, and any other damage. Exclusion criteria are mouthwash the same day, antibiotics in past 30 days, daily antivirals, and eating or drinking 1-hour preceding collection. Inclusion criteria are a definitive diagnosis of MS, age 18-74 years old, and either White or African American. After collection, saliva is sequenced for 16S ribosomal RNA and screened for metabolites by mass spectroscopy.Data analysis:Statistical methods: Principal component analysis (PCA) to compare groups, unpaired t-tests to compare means, and pathway analysis to identify altered metabolic pathways.

Results: To date, 16 MS subjects and 9 controls were analyzed. Comparison of bacterial taxa (phylum to species) between the MS cohort versus the control cohort showed several differences without reaching significance. However, comparison of White males (MS to control) (Figure 1) shows significantly increased phylum Firmicutes in MS patients and almost significant reduced Proteobacteria. Further comparisons are in progress. Untargeted metabolite screening on all samples and PCA shows that the 2 groups are distinct, aside from 3 outliers in the MS and control groups (Figure 1). There are about 450 metabolites significantly different between the 2 groups, and pathway analysis points to folate (Vitamin B12) metabolism and one-carbon pool for methylation processes. A targeted analysis for differences in small chain fatty acids (SCFAs), which can affect T-cell functions, identified an almost significant increase in isovaleric acid in the MS cohort. Comparisons to compare White males (MS, n = 3 to control, n = 6 including Hispanic White) found about 250 significantly different metabolites, and pathway analysis again points to folate metabolism.

Conclusions: Initial results indicate significant differences in the oral microbiome between MS and controls independent of gender or race. Differences in sub-cohorts require larger groups to confirm significance. Similarly, we identified many metabolites significantly altered in MS versus controls, with changes in folate, which can be metabolized by bacteria and can regulate systemic inflammatory processes. Together, these findings confirm that the oral microbiome differs between MS and controls along active metabolites. The OMS can play a key role in assisting the neurology team in evaluation, specimen procurement, and potential recognition of aggravating odontogenic issues, which may assist in management of the MS patient.ReferencesBouftas M. A Systematic Review on the Feasibility of Salivary Biomarkers for Alzheimer's Disease. J Prev Alzheimers Dis 2021, 8:84-91.Boullerne AI et al. Deep DNA metagenomic sequencing reveals oral microbiome divergence between monozygotic twins discordant for multiple sclerosis severity. J Neuroimmunol. 2020, 343:577237.

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